error when users try to unsubscribe

I have a few WP sites that use this plugin and it seems to function fine until someone tries to unsubscribe. They receive the following error.

Warning: Cannot modify header information - headers already sent by (output started at /var/www/wordpress/wp-content/plugins/subscribe-by-email/subscribe-by-email.php:262) in /var/www/wordpress/wp-includes/pluggable.php on line 934

I have tried subscribing and then unsubscribing myself from 2 of our sites and get the same error. We are running WP 3.2.1 and I have tried replacing the subscribe-by-email.php file with a new one and have also deactivated and reactivated the plugin.

I disabled all of plugins for the site and an all of network activated plugins with the exception of subscribe-by-email . I also move all of the plugins out of the mu-plugins directory. Unfortunately I'm still getting an error. I thought maybe it was the theme but 2 of the sites are using different themes. One is using Magazine Basic and the other is using Connections

I just checked both files and made sure there isn't any empty spaces at the top or bottom of the files. I also moved out the existing subscribe-by-email directory and loaded a whole new directory and all of the files that I just download off of your site. Still no luck.

Notice: Undefined index: action in /var/www/blogs/wp-content/plugins/subscribe-by-email/subscribe-by-email.php on line 259

Notice: Undefined index: action in /var/www/blogs/wp-content/plugins/subscribe-by-email/subscribe-by-email.php on line 282

Notice: Undefined index: action in /var/www/blogs/wp-content/plugins/subscribe-by-email/subscribe-by-email.php on line 270

Notice: Undefined index: action in /var/www/blogs/wp-content/plugins/subscribe-by-email/subscribe-by-email.php on line 276

Warning: Cannot modify header information - headers already sent by (output started at /var/www/blogs/wp-includes/functions.php:3466) in /var/www/blogs/wp-includes/pluggable.php on line 934

I also get

Notice: define() was called with an argument that is deprecated since version 3.0! The constant VHOST is deprecated. Use the boolean constant SUBDOMAIN_INSTALL in wp-config.php to enable a subdomain configuration. Use is_subdomain_install() to check whether a subdomain configuration is enabled. in /var/www/blogs/wp-includes/functions.php on line 3466

so I tried changing the define('VHOST', 'no'); to ('SUBDOMAIN_INSTALL' ,'no'); but then none of my sites existed.

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